Dampers of the type in question here are also referred to as absorbers and resonators. Reference is made, by way of example, to DE 198 55 708 B4, DE 10 2008 032 491 A1 and DE 10 2010 042 893. Such dampers have proven successful in practice. They make it possible to avoid disturbing noises in the area of the charge-air line. The dampers can be produced in induction systems to match the available installation space. However, there is not always sufficient space available for the dampers; the required volumes are often not sufficient for the design of the sound dampers. It is therefore endeavored to make the dampers as small as possible and to make them match existing intermediate spaces between other components of the internal combustion engine as optimally as possible.
EP 761413 B1 discloses a method for producing a damper from plastic by extrusion blow molding. In this case, a preform is first extruded in an open mold. Then, after closing the mold, part of the mold is opened at a place at which an accessory is to be molded, and an extension of the preform is first formed at the place at which the mold is open, in a first blow-molding step. Then the previously open part of the mold is closed by another mold piece, which is adapted to the extension, and a second blow-molding operation is carried out, whereby the final form is achieved.
EP 701 083 B1 describes a connection tube with a chamber attached laterally to it. It also describes a method for producing such a component comprising a connection tube and a chamber.
DE 69 604 195 T3 discloses a method for producing a sound damper in which a first part of the housing is produced from plastic and a second part of the housing is produced from plastic and these two parts are subsequently connected to one another. A blow-molding operation does not take place.
Dampers of the type mentioned at the beginning are mainly used for internal combustion engines having turbochargers. These internal combustion engines have a relatively small swept volume, and consequently also relatively small dimensions. The relatively small dimensions lead to relatively small installation spaces for the individual parts, for example also for the dampers. The space available for the sound absorption is therefore small.
The operating noises emitted by the internal combustion engine are expected to meet prescribed requirements. It is desired that the engine sounds as good as possible. In the case of turbocharged engines, one of the reasons for noises to occur is the distribution of the charge air within a turbocharger. There are other noises in addition to this. Those noises that are within the human audible range are to be damped in particular. A desired noise emission that is favorable for the internal combustion engine and for the car is to be achieved. To do so, engine developers are increasingly demanding sound reduction in wide frequency ranges.
For prior art, reference is made generally to the German book by the authors Michael Thielen, Klaus Hartwig and Peter Gust “Blasformen von Kunststoff-Hohlkörpern” [Blow-molding of plastic hollow bodies], Hanser-Verlag 2006.
Among the processes that are used today for the production of such dampers, for example the damper according to DE 198 55 708 B4, is that known as hydroforming. In this way, outer jackets with one or more volume chambers can be produced in sheet metal. However, these outer jackets still have to be connected, for example welded or brazed, to further components in order to obtain a complete damper. Moreover, a tightness test also has to be carried out.